This invention relates to a filamentary film construct which is used in providing cementitious mixtures supplemental and reinforcing strength upon setting, and more particularly, to a unitized filamentary construct which comprises a plurality of oriented reinforcing filamentary film components, which may comprise fibrillated film, combined with a circumferential retaining element, said circumferential retaining element providing temporary retention of the oriented reinforcing fibrous components until such point the unitized fibrous substrate is incorporated and subjected to mechanical agitation during preparation of a cementitious blend or mixture.